Furniture door hinges are known which comprise first and second fastening elements, connected to each other by inner and outer link elements, each of which is articulated at one of its ends to the first fastening element and at its other end to the second fastening element. The outer link element executes a swivelling movement in two opposite directions on each complete opening or closing movement of the hinge and has a curved face which is partially cylindrical concentric with and disposed at a spacing from its fixed articulation axis and a vertex being disposed at one end of the curved face. A spring element acting on said lank element remains inactive when it is seated against the curved face end pushes the hinge into its closed position when it leaves the curved face.
In this type of known hinge the first fastening element is fixed to the body of the piece of furniture and the second fastening element is fastened to a door, and both fastening elements are attached to each other via the link elements to form a four-bar linkage acting in such a way That the door not only swings about a vertical axis when opened, but also at the same time projects beyond the front face of the piece of furniture and is displaced laterally in relation to the side edge of the latter. By this means a door placed on the front face of a piece of furniture takes up no space at the side near the body of the piece end cannot bump into immediately adjacent doors or drawers when it is opened.
A hinge of this known type is discharged in DE-C2-25 39 197. The curved face is disposed on two projections which project approximately et right angles into the first fastening element in the region of the fixed hinge pin of the outer link element. Rollers roll on these projections, and ere mounted on the ends of a spring which is located in the first fastening element and which holds the hinge in its closed position when the rollers disposed at the ends of the spring roll over the vertex and press laterally against the projections. Using this known hinge, the door can only be held in its closed position by the hinge. As soon as the spring rollers have ridden over the vertex on the projections of the outer link element, the door leaf can swing freely to end fro into its fully open position. This has the disadvantage that even fully open doors of pieces of furniture which are not exactly vertical can close again by themselves.
The known hinge also requires much space, since the projections which extend into the first fastening element and the spring acting on these projections are disposed behind one another in the longitudinal direction of the fastening element. Moreover the spring, which only serves to hold the hinge in its closed position, is costly to manufacture and difficult to install. In addition, the rollers et the free ends of the spring require a free-swinging axial pin and a lateral guide if they are not to slide off the curved faces. Furthermore, if the spring is constructed as a coil spring, it requires an additional bearing pin in the first fastening element of the hinge.
A hinge is also already known (U.S. Pat. No. 4 114 237) in which the free active leg of a leg spring slides along the back of the inner link element, which has a partially cylindrical curved face and a stop face disposed approximately perpendicularly thereto. In the closed position of the hinge the spring leg presses against the stop face and produces a torsional moment, which pushes the inner link element, and thereby also the second fastening element which is fixed to the door, into its closed position, and in this manner holds the door in its closed position. On opening the door, the spring leg surmounts the vertex between the stop face and the curved face. It then makes contact with the curved face and acts radially in relation to the fixed hinge pin of the inner link element, whereby it cannot exert a torsional moment on the latter. The movable, second fastening element and the furniture door fastened thereto can then be swung their open position or closed position without the application of force. In order also to hold the door in its open position to a certain extent, a latching recess, into which the free spring leg can slide, is provided on the partially cylindrical curved face which is concentric with the fixed hinge pin.
With this known hinge there is a risk that the free spring leg will pass through the latching recess on opening the door, whereupon the hinge pins of the hinge together with the link elements mounted on it have to absorb the inertial forces due to the torsional moment of the opening door, which can be quite considerable under some circumstances, and they may easily be damaged under these circumstances. In particular, the known hinge is only capable of functioning if the free spring leg of the leg spring is provided with a roller, which rolls on the back of the inner guide lever when the movable, second fastening element swivels. Since the leg spring requires a high initial stress in order to fulfil its holding function when the hinge is closed, and the hinge is also of relatively complicated construction, there are difficulties associated with mounting and guiding the tracking roller. However, without a tracking roller such as this the free spring leg is subjected to a very high level of wear, as are the curved face and the stop face. This is because the spring leg covers a relatively long path on the stop face and on the curved face on opening and closing the door, and the contact surfaces ere only small, so that a high specific contact pressure is transmitted from the spring leg to the curved face and the stop face. This wear is so high that a hinge without a tracking roller may even become unserviceable after a short period of use.
A hinge is also already known U.S. Pat. No. 4 065 829) by means of which a door which is fitted with it is held by the force of a spring both in its closed position and in its open position. The spring force is produced by a C-shaped leaf spring or spiral spring, which can bear on the fixed hinge pin of the inner lank element, and which exerts a permanent effective pressure on a projection on the outer link element. By this means the known hinge is permanently pushed either into the fully closed position or into the fully open position. A door fitted with this known hinge therefore has no intermediate position, but permanently either opens or closes, which in general is undesirable.